Random Search in SYBYL- Symmetry option

        I would like to know the effect of symmetry option on and off on random
 search in Sybyl.
 > From Tripos bookshelf and the references mentioned it is clear to me how
 search works and check chirality option functions but I do not understand how
 check symmetry option works.
 Thank you very much in advance.
 Deepangi Pandit